Burning postharvest sugarcane residue is a standard practice to remove extraneous leaf material before spring regrowth. Live-fires were simulated from field-collected postharvest sugarcane residue and seeds of divine nightshade and itchgrass were exposed to dry and moistened postharvest residue (PHR) at four densities (6.1, 12.1, 18.2, and 24.2 Mg ha−1) and a nonburned control. The moisture content of residue exposed to simulated rainfall was 14% more in Experiment 2 than Experiment 1; however, burning PHR with 44% moisture when wind speeds were lower allowed the fire to continue and created a smoldering effect that reduced weed emergence by 23% when compared with burning PHR with 30% moisture during breezy conditions. The moistened 6.1 Mg ha−1 PHR treatment resulted in 53% more divine nightshade and itchgrass emergence when compared with dry 6.1 Mg ha−1 PHR after burning, and greater emergence was attributed to more seed survival for divine nightshade than itchgrass. The PHR moisture condition failed to influence the burn duration; however, the burn duration increased 103% and 56% as the amount of PHR increased from 6.1 to 12.1 Mg ha−1 and 12.1 to 18.2 Mg ha−1, respectively. The combination of high wind speeds and moistened PHR did not enhance the maximum burn temperature near the soil surface, but surface-deposited divine nightshade and itchgrass seeds were susceptible to prolonged exposure times at 100 C. Burning PHR from fields with poor stands or older ratoon, especially when PHR is abundantly wet, will not produce temperatures lethal to divine nightshade and itchgrass seeds. The fluid-filled and fleshy content that comprises divine nightshade fruit protected seed from short durations of high temperatures, but may not insulate seeds long enough when exposed to a smoldering fire.

Brush control and woody plant community structure in the Cross Timbers of Oklahoma resulting from treatments with herbicides and fire were compared. Tebuthiuron and triclopyr were applied alone and in combination with burning at 2.2 kg ai ha-1 in March and June of 1983, respectively. The burned pastures were burned with strip headfires in late spring of 1985, 1986, and 1987. Both herbicides were effective on the dominant overstory brush species, blackjack oak and post oak, and this resulted in good reduction of canopy cover of brush initially. However, effects of triclopyr were short-lived because of ineffectiveness on many of the other hardwood species (American elm, gum bumelia, hackberry, roughleaf dogwood, and buckbrush). Crown reduction and tree kill of these hardwood species was usually better with tebuthiuron than with triclopyr. Neither herbicide was effective on eastern redcedar. Better brush control, associated with tebuthiuron, resulted in better fine fuel release and by 1988, burning was having a significant effect on woody plants in the tebuthiuron-treated plots.

Woody plant encroachment restricts forage production and capacity to produce grazing livestock. Biophysical plant growth simulation and economic simulation were used to evaluate a prescribed burning range management technique. Modeling systems incorporated management practices and costs, historical climate data, vegetation and soil inventories, livestock production data, and historical regional livestock prices. The process compared baseline non-treatment return estimates to expected change in livestock returns resulting from prescribed burning. Stochastic analyses of production and price variability produced estimates of greater net returns resulting from use of prescribed burning relative to the baseline.

Burning and 2,4-D [(2,4-dichlorophenoxy)acetic acid] were used on the early stages of beaked hazel (Corylus cornuta Marsh.) understory to prevent development of a dense, continuous understory. At this early stage beaked hazel understories consisted of seedlings, small clones, and large clones. The application of 1.12 kg/ha of 2,4-D in July and August killed 84 to 100% of the seedlings and small clones, 86 to 98% percent of the large clones; while the application of 0.56 kg/ha of 2,4-D in June, July, or August caused 77 to 98% mortality of seedlings and small clones, but only 57 to 83% of large clones. Effects of burning were much more variable and generally mortality was less than with 2,4-D. One or two burns killed 23 to 100% of seedlings and small clones, and an average of only 13% (range 0 to 93%) of large clones.

Understory vegetation was studied following treatment by herbicides and fire on grazed pastures within the Cross Timbers vegetation type. Tebuthiuron and triclopyr at 2.2 kg ha-1 were applied in March and June of 1983, respectively. The pastures were burned in late spring of 1985, 1986 and 1987. Frequency of horseweed, rosette panicgrass, and little bluestem increased with both herbicides, but the increase was usually larger with tebuthiuron than triclopyr. Burning as a follow-up to either herbicide had little effect on frequency of rosette panicgrass and little bluestem. Horseweed increased following burning in 1985 and 1987. Standing crop of grasses and forbs increased dramatically following herbicide treatments. Grass production was greater with tebuthiuron, whereas production of forbs and browse was generally greater with triclopyr.

Medusahead is one of the most problematic rangeland weeds in the western United States. In previous studies, prescribed burning has been used successfully to control medusahead in some situations, but burning has failed in other circumstances. In this study, trials were conducted using the same protocol at four locations in central to northern California to evaluate plant community response to two consecutive years of summer burning and to determine the conditions resulting in successful medusahead control. During 2002 through 2003 large-scale experiments were established at two low-elevation, warm-winter sites (Fresno and Yolo counties) and two higher elevation, cool-winter sites (Siskiyou and Modoc counties). Plant species cover was estimated using point-intercept transects, and biomass samples were taken in each plot. After 2 yr of burning, medusahead cover was reduced by 99, 96, and 93% for Fresno, Yolo, and Siskiyou counties, respectively, compared to unburned control plots. Other annual grasses were also reduced, but less severely, and broadleaf species increased at all three sites. In contrast, 2 yr of burning resulted in a 55% increase in medusahead at the coolest winter site in Modoc County. In the second season after the final burn, medusahead cover remained low in burned plots at Fresno and Yolo counties (1 and 12% of cover in unburned controls, respectively), but at the Siskiyou site medusahead recovered to 45% relative to untreated controls. The success of prescribed burning was correlated with biomass of annual grasses, excluding medusahead, preceding a burn treatment. It is hypothesized that greater production of combustible forage resulted in increased fire intensity and greater seed mortality in exposed inflorescences. These results demonstrate that burning can be an effective control strategy for medusahead in low elevation, warm-winter areas characterized by high annual grass biomass production, but may not be successful in semiarid cool winter areas.

Cogongrass [Imperata cylindrica (L.) Beauv.] is a warm-season, rhizomatous grass native to southeast Asia that has invaded thousands of hectares in the southeastern United States. Its negative impacts on pine forests have been well documented, and aggressive control is widely recommended. Although repeated herbicide treatments are effective for suppression, integrated strategies of prescribed burning coupled with herbicide treatment and revegetation are lacking in pine systems. In particular, longleaf pine forests, which are typically open, fire-dependent, communities, are highly susceptible to cogongrass, which is a pyrogenic species. To address management goals for cogongrass control and herbaceous restoration in longleaf pine forests better, field studies were conducted in southwestern Alabama from 2010 to 2012. Two longleaf pine forests with near-monotypic stands of cogongrass in the understory were selected for study. Treatments included combinations of winter prescribed fire, spring and fall glyphosate herbicide treatments, and seeding a mix of native, herbaceous species. Data were collected for three growing seasons following study initiation, and included seasonal herbaceous species cover and final cogongrass shoot and rhizome biomass. Species richness and diversity were calculated and analyzed to ascertain treatment effects over the duration of the study. Burning slightly improved cogongrass control with glyphosate, but had no effect on total cover, species richness, or species diversity. Three glyphosate treatments reduced total vegetative cover and nearly eliminated cogongrass cover, shoot, and rhizome biomass. Glyphosate and glyphosate + seeding also increased herbaceous species richness and diversity. However, aboveground productivity in treated plots was significantly lower than productivity in the untreated control, which was almost exclusively cogongrass. These studies indicate that glyphosate and integrated strategies utilizing glyphosate and seeding are very useful for cogongrass management and increasing herbaceous species richness and diversity in longleaf pine.

Paragrass is a nonnative category I invasive species in central and south Florida. This perennial grass species outcompetes native vegetation and is capable of rapid spread by vegetative reproduction. Although glyphosate and imazapyr are effective herbicides for paragrass control, the use of herbicides in certain areas may be restricted because of application timing or environmental concerns. Therefore, our objectives were to examine the effect of water depth (saturated vs. flooded) after burning or cutting, and the effect of water depth and duration after simulated roller-chopping, on paragrass regrowth under controlled conditions. In the first study, paragrass plants were cut or burned with a propane burner to 1 cm (0.39 in) above the soil surface. Plants were either watered daily (control), or were subjected to one of two water treatments: water level at the soil surface (saturated) or flooded to a depth of 44 cm. Burned-saturated or burned-flooded plants had 92% less biomass 5 wk after treatment (WAT) than cut-saturated plants. Flooding resulted in plant death regardless of the plant treatment. In the second study, simulated roller-chopping was performed by cutting paragrass stolons into one-, two-, or three-node segments; planting them into flats; and subjecting them to water treatments for 3, 7, 14, 28, and 42 d. Burning, cutting, and roller-chopping could be useful to control paragrass if subsequent flooding is applied. Future research should focus on evaluating the response of these control techniques in natural areas where water depth can be managed.

Pollen analysis of a 9.03-m-long lake sediment core from Pender Island on the south coast of British Columbia was used to reconstruct the island's vegetation history over the last 10,000 years. The early Holocene was characterized by open mixed woodlands with abundant Pseudotsuga menziesii and a diverse understory including Salix and Rosaceae shrubs and Pteridium aquilinum ferns. The establishment of Quercus garryana savanna-woodland with P. menziesii and Acer macrophyllum followed deposition of the Mazama tephra until ~ 5500 cal yr BP, when these communities gave way to modern mixed P. menziesii forest. Charcoal analyses of the uppermost sediments revealed low charcoal accumulation over the last 1300 years with a mean fire return interval (mFRI) of 88 years. Fires were more frequent (mFRI = 50 yr) during the Medieval Climate Anomaly (MCA) with warm, dry conditions facilitating a higher fire frequency than during the Little Ice Age, when fires were infrequent. Given the projected warming for the next 50–100 years, land managers considering the reintroduction of fire to the Gulf Islands National Park Reserve may want to consider using the mFRI of the MCA as a baseline reference in prescribed burning strategies.

Restoration of historic fire regimes is complicated by concerns about exotic plant invasions, yet little is known of how the two may interact. Seeds of Japanese brome, spotted knapweed, Russian knapweed, and leafy spurge were subjected to fire at six fuel loads (100 to 700 g m−2) and a nonburned control. Fires were simulated with field-cured grass and time–temperature profiles were developed from thermocouples at the soil surface. Emergence was determined by species and fuel load in growth chambers. Fuel load explained 98% of variation in mean heat dosage and emergence decreased with increasing fuel load across species. Emergence was reduced 79 to 88% relative to nonburned treatment with 100 g m−2 of fuel and at least 97% with 200 g m−2 of fuel. Emergence probabilities were less than 0.01 for all species but spotted knapweed with a 300 g m−2 fuel load. Results indicate high potential for fire to disrupt the life cycle of invasive species through direct seed mortality. The relationship between fuel load and seedling emergence provides good predictability of fire effects on surface-deposited seeds. A single fire is unlikely to eradicate many invasive species because they often produce abundant seeds and some will undoubtedly escape fire. However, abrupt reductions in seedling emergence with relatively light fuel loads indicate that fire may be an effective tool for increasing mortality of invasive plant seed across a broad range of habitats.

Prescribed burning can control invasive annual grasses that threaten the biological and economic value of California grasslands. Susceptibility of grass seed to burning can depend on burn timing, exposure time, and type of exposure (direct flame heat or convective heat); thus, these factors can influence the success of a prescribed burning program. To further investigate these factors, laboratory simulations were conducted on barb goatgrass, medusahead, and ripgut brome at several stages of seed maturity, as determined by percent moisture of the inflorescences. Seeds were exposed either to direct flame using a Bunsen burner or to heated air in a muffle furnace. Flame treatments were conducted at one temperature (∼400 C) and several exposure times (0 to 14 s), depending on the species. Furnace treatments included four temperatures (150, 200, 250, and 300 C) and seven exposure times (0, 10, 20, 30, 40, 60, or 80 s). Seed germination was analyzed for each temperature series to determine the LD50 and LD90 in seconds of exposure time. Susceptibility to furnace treatments, which simulated heat exposure of seeds on the soil surface, was not statistically different within a range of seed moisture levels for all three species. The LD50 values at 250 C (typical soil temperature with grassland fire) ranged from 28 to 49 s, which far exceeds the time of exposure during a typical grassland fire. Susceptibility to flame showed a similar lack of change over maturation of medusahead and barb goatgrass seeds, with LD90 values ranging between 4.8 and 7.4 s for all seed moisture levels. In contrast, ripgut brome seeds exposed to flame showed increasing susceptibility with reduced seed moisture content. The LD90 values for exposure were less than one second for seed moisture levels at or below 10%, compared to 3.7 s for seeds at 55 to 60%. Although flame susceptibility increased for ripgut brome, seeds at all maturation stages were more sensitive than medusahead and barb goatgrass. Additionally, the LD90 values for all three species are attainable under field conditions. Thus, burn prescriptions for these three species are not constrained by maturation stage, but should occur prior to seed drop and when fuel loading is high. This will maximize exposure time of seeds to direct flame.

Macartney rose is a range management problem on 500,000 acres of rangeland in Texas. Roller chopping followed by burning is an effective method of improving infested rangeland. However, uncertainty associated with implementing effective burns adversely affects economic feasibility of the treatment sequence. Discrete stochastic programming is used to determine optimal burning schedules under uncertainty. Optimal schedules and expected net returns vary with changes in the probability of a successful burn.